Three male British teenagers allegedly seeking to join Islamic State extremists in Syria have been arrested in London, after being deported from Turkey.

Scotland Yard police on Sunday did not identify the three suspects, but said they were detained Friday in the Turkish city of Istanbul. Turkish media reports say the trio -- two age 17 from northwest London and a third age 19 -- were arrested after a flight from Barcelona.

All three face charges of violating Britain's 2006 Terrorism Act.

Turkish sources say the 17-year-olds were arrested after tips from British authorities, while the 19-year-old was detained after questioning by airport police.

These arrests come just weeks after three British schoolgirls gained international attention by fleeing London for Istanbul. Days later, Turkish authorities said the girls had crossed into war-torn Syria and likely joined the extremist group.

Western security analysts estimate that 600 young Britons have gone to Syria or Iraq to join militant groups, including the purported executioner featured in Islamic State videos showing beheadings of hostages.

In revised figures released last month, U.S. analysts say 20,000 foreign fighters from 19 countries have joined Islamic State, including at least 3,400 recruits from Western countries.